Threaded fasteners are not designed to operate under shearing loads except in the unthreaded portion. Generally, for tension loads there needs to be at least three theads in FULL engagement which usually means at least five threads entering the hole.
Whilst the clamping forces exerted on most commercial bases holds things together fairly well (kind thoughts help, I reckon), I've seen plenty of U/S mounting screws on rifles that no longer hold zero. Plus, one of my L42a1's had its front pad screws severly joggled after an apparent solder failure. The initial firing session displayed rather poor shooting capabilities;the problem wasn't detectable until the screws were loosened-they were all so offset that it was difficult to remove from the pad. (Very rectified now!-Unfortunately a friend has it back after a convoluted trade.)
That's enough ranting from me... Back to Enfields!